>
> I've thought of that, but mine is cast iron - it has way too much
> thermal mass to be accurately controlled ∗at all∗. It takes about
> three minutes to get up to temperature, and the ramp-up is pretty good
> for reflow soldering, so as long as I don't mess with it it works for
> one board at a time, or multiple boards simultaneously, just not for
> multiple boards consecutively.
>
> If I'm going to start hacking up an mcu-controlled reflow device, I
> won't start with a cast iron hotplate.
>
Thermal mass is no problem, it actually makes it easier, you just have to tune your temperature control to what you're controlling. With electronic control you aren't limited to long on/off cycles with loads of hysteresis, you can cycle the heater rapidly or even use phase angle control (think light dimmer) to vary the power to the heater. It can be done with a few op-amps and a handful of passives, or you can use the microcontroller of your choice.
My 400 gallon spa has a lot more thermal mass than your hot plate, and it has no trouble maintaining the temperature to within a fraction of a degree.